This control for 12 V drills was found in a 90s Elektor. The components are current, and Q1 can be replaced by a TIP42 mounted on a heat radiator.
The transistor of this circuit found in an old American documentation can be the BC548 for T1 and...
This circuit was found in Motorola documentation from 1969. The transistors are from that time. The...
The crystal in this circuit can have frequencies from 100kHz to 8MHz. Capacitor C2 adjusts the...